I was told to post here.. I asked for some help first in the programming section as I was trying to time the delay of the system I had.(original post http://arduino.cc/forum/index.php?topic=118770.new;topicseen#new )

My first "big" arduino project... using salvaged parts to make a lightning trigger.

A tiny solar cell from a DOA solar thermometer..An optical isolator from a powersupplya potentiometer scavenged from a tv aerial booster...a couple of other bits & pieces...

sbright33

I have built a circuit to detect sound, but this does not help, obviously. For lightning I keep the shutter open for 10-30s in the dark. Hoping to catch multiple flashes. Do this over and over. Quickly scan thru the images on a PC to find the good ones. When it's light you have to use a shorter time with a narrow aperture. You can close the shutter after the lightning to increase the contrast. A simple sketch might tell me how many good pictures I have if I'm not concentrating by counting the flashes. It could tell me the image number to look at. It could close the shutter. But I don't see how to use it as a trigger.

focalist

The delay in that shutter opening varies between cameras, but luckily Lightning is usually a pretty complex event with multiple cloud to ground and return strokes.. it's not uncommon for a stroke of lightning to last up to half a second. Since the ionization pathway is usually the same for the return stroke, even though you miss the start of the cloud to ground stroke, you will most likely make up for it with the return and subsequent discharge strokes on the pathway. Going back in time isn't necessary because the event duration is long enough and repeated multiple times, even if our eyes don't SEE it that way.

I've not done a lightning trigger yet, but they are easy to make and do work well. The best alternative (which isn't any better) is to stop down the lens and do repeated time exposures hoping for a strike during any particular exposure period. I've done this, and though it works, it tends to produce washed-out images, even if the "beginning" of the stroke is captured. The contrast captured above is far superior to what can be gotten by doing time exposures, including motion blur of moving clouds and incident lighting from other lightning occurring within the storm but not directly visible as strokes to the eye or camera, just diffuse flash carried through the cloud. By making a short exposure, the contrast and sharpness can be kept, particularly since a large aperture and slow ISO can be used.

sbright33

Great discussion! But you do miss the first 250ms with a T2i. I would like to capture that, but as I stated it is impossible using the traditional method. An instant trigger would produce an interesting image that you cannot get no matter how many times you wait 1/4 sec.

Great discussion! But you do miss the first 250ms with a T2i. I would like to capture that, but as I stated it is impossible using the traditional method. An instant trigger would produce an interesting image that you cannot get no matter how many times you wait 1/4 sec.

Well given shutters are mostly mechanical devices, it does take some time to physically move the shutter. There are a few cameras with electronic shutters that should be faster.

My Olympus SP-550UZ from a few years ago has a pre-capture mode when it is in 15 frames/second mode. In that mode, the picture size is reduced to 1280x960, and as long as you hold the shutter down 1/2 way (usually used for pre-focus), the camera will continuously record pictures in internal memory. When you complete the shutter press, the camera will dump the last 5 pictures into the memory card, as well as 15-20 pictures afterwards. The Olympus SP-550UZ does support the RM-UC1 shutter release, so it could be controllable via an Arduino. Hmmm, I should try this sometime. Unfortunately, I think Olympus only supported pre-capture for a few of the SP series of cameras (SP-550UZ through SP-590UZ, as well as the E-100RS from over 10 years ago). I haven't used my SP-550UZ for about 2 years now other than quick tests.

sbright33

Magic Lantern allows you to take "video" at 1-4fps. The shutter is always open. This would let enough light in for lightning and allow you to capture hours worth of data without missing anything. Still I prefer my 10 second exposure. To increase contrast you close the shutter AFTER the lightning flash.

focalist

I won't have time to finish it up until next week at the earliest, but I'm in the process of making a shutter trigger which uses a phototransistor not mounted externally, but mounting it so the phototransistor is IN the viewfinder- the idea being that I can set a particular scene and the camera will trigger with any large (adjustable) change in the overall brightness "seen" by the phototransistor. My intended target with this is to get some wildlife shots, but it would work for lightning also-- anything that will change the overall illumination through the lens ought to do the job..